In the electronics industry, a continuing objective is to further and further reduce the size of electronic devices while simultaneously increasing performance and speed. To accomplish this, increased miniaturization of integrated circuit (“IC”) packages for these devices is becoming increasingly essential. Cellular telephones, personal data devices, notebook computers, portable music players, camcorders, and digital cameras are but a few of the consumer products that require and benefit from this ongoing miniaturization of sophisticated electronics.
IC assemblies for such complex electronic systems typically have a large number of interconnected IC chips, or dies. The IC dies are usually made from a semiconductor material such as silicon (Si) or gallium arsenide (GaAs). During manufacture, the several semiconductor devices on the IC dies are formed on the dies in various layers using photolithographic techniques.
After manufacture, the IC dies are typically incorporated into IC packages that may contain one or several such dies. Typically, a die is mounted on the surface of a substrate by a layer of epoxy, and electrical contact pads on the upper surface of the die are then connected to the substrate by gold bond wires. Solder balls can also be provided on the lower surface of the die for additional connections between the die and the substrate. A molding compound then encapsulates the die and the bond wires, providing environmental protection and defining the semiconductor IC package. These IC packages, or modules, are then typically mounted on printed circuit boards.
Heat management through such an IC package structure can be critical. The internal thermal resistance and thermal performance of the packaged die are determined by a series of heat flow paths. By making high heat conductivity connections between the bottom of the die and the package substrate, the heat generated by the die can be transferred efficiently from the die to the substrate and then out of the IC package. Often, however, the amount of heat generated in the die is more than can be efficiently transferred in this manner, thus requiring the attachment of a heat spreader to the top of the IC package.
With the ever-decreasing sizes of electronic devices, die-sized IC packages have been developed in which the dimensions of the IC package are almost the same as those of the semiconductor die that is encapsulated inside the IC package. Such “near-chip-scale” or “near-die-scale” packages (typically up to 17 mm×17 mm) also have low profiles (ranging up to 1.70 mm). Some near-die-scale IC package configurations are molded together in arrays and then separated from one another by saw singulation along the edge lines of the packages. Others are molded individually. Both package designs provide acceptable thermal performance for low power semiconductor devices.
Increasingly, however, higher heat dissipation is needed as device-operating frequencies increase and as devices become progressively denser and more integrated. One solution has been to attach an external heat spreader to the package. Another solution, for individually molded packages, has been to include a “drop-in” heat spreader that is embedded within the package. The “drop-in” heat spreader is so named because it can be fabricated by dropping the heat spreaders into the individual mold cavities prior to molding the packages therein.
With array-molded packages, however, it is very difficult to cost-effectively mold heat spreaders into near-die-scale IC packages. The heat spreaders must be held precisely in position during the molding process and cannot be allowed to interfere with the proper flow of the mold plastic or resin into and through the mold during the molding process. The heat spreaders also must not tear or interfere with the sawing operation when the packages are singulated following the molding operation.
These problems are made even worse by modern, high-performance package configurations. For example, in an effort to improve downward heat conduction to the motherboard, thermally conductive epoxy molding compounds (“EMCs”) and multi-layer substrates have been used. However, thermally conductive EMCs are expensive and difficult to process. Moreover, their high filler content increases stresses in the IC packages and on the die surfaces. Multi-layer substrates are also expensive, and they remove heat only through the motherboard. Therefore, internal package heat spreaders may still be needed for such package configurations, especially for a motherboard that has several heat-generating IC packages thereon.
Thus, a need remains for economical, readily manufacturable heat spreaders for small, array-molded, near-die-scale IC packages, and particularly for heat spreaders that can be easily embedded directly within such packages. In view of the ever-increasing need to reduce costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.